Wood as a material of natural origin, as with all organic materials, is subject to microbiologically caused decay. In addition to Basidiomycetes, molds, yeasts and, in rare cases bacteria also, contribute to this decay. Particularly in a moist environment, wood is susceptible to said decay-causing organisms.
The decay-causing organisms also include various wood-staining fungi, which can grow relatively rapidly on wood surfaces which are freshly cut and/or exposed to weathering. This also relates to wood which must be stored under unfavorable conditions, for example in the forest after felling, or under tarpaulins after processing, in particular during transport. The staining, which can be caused, for example, by Aureobasidium pullulans is frequent on untreated wood. It is known under the name “blue stain”. The presence of such fungi can lead not only to impairment of the appearance of wood or articles produced therefrom, but there is also the hazard that fungi or toxins formed by these can transfer from the wood to other products and that even long-lasting forms of the molds can be given off into the surrounding air. Inspiring such fungi can, in the case of sensitized people, lead to asthma attacks, for example. In addition, the wood is also adversely affected in value, so that infected wood has only a low value or must be destroyed.
For reasons simply of product and consumer protection, a protective treatment is virtually inescapable.
In the timber industry, various wood preservatives are used. Frequently, the constituents of these wood preservatives are substances which are associated with considerable health risk. For example: fluorine compounds (such as copper hexafluoro-silicate, potassium hydrogen fluoride, ammonium hydrogen fluoride), arsenic compounds (principally arsenic pentoxide), boron compounds (such as boric acid, polyboron), copper compounds (for example copper sulfate), tin compounds etc. The chromium compounds which are also used (such as potassium chromate, ammonium dichromate), are no longer biocides in the real sense, since these serve for fixing the biocides in the timber.
The majority of these substances, in accordance with the German dangerous substances ordinance, are toxic or at least hazardous to health. In addition to the odor nuisance due to intensely odorous wood preservatives such as wood tar oils, which is still to be classified as harmless, considerable harm to health can occur merely by contact with some of the abovementioned wood preservatives or correspondingly treated wood.
Despite the required occupational safety measures when such wood treatment agents are used in the industrial sector, the user of wood thus treated frequently is not informed about the possible health risks of direct contact with wood thus treated. In the event of long-lasting direct contact with this wood, the risk of delayed harm to health cannot be excluded.
In addition to the use of such materials in the industrial sector, therefore, use by craftsmen in the house and home sectors is particularly a problem.
Particularly strict measures must be applied to wood which can come into contact with foods, food ingredients, food-contact articles, animal feeds, pet food, cosmetics, food wastes or articles of daily use in the broadest sense. In this case there is always the possibility of direct transfer to these articles, for example foods. Such a transfer must always be avoided in the case of materials which are not suitable for consumption or are even toxic, in order to exclude health risks. However, because it is known that unintentional or indirect contamination cannot be absolutely excluded, it is an object of the invention to achieve sufficient protection of the wood from mold attack, without risks to health resulting from contact with the wood or transfer of the wood preservative to other products such as foods.
Preservatives which are used to preserve various foods have occasionally also been tested for their applicability to preserving wood, in particular in the form of derivatives which are not used as such for food preservation. Some inventions take on this problem and use various acids, some in combination with other substances, for treating wood. Thus, DE-A 100 03 170 (=EP-A 1 123 787) uses sorbic acid and its salts for protecting wood from mold attack. DE-A 197 03 552 describes mold-inhibiting aqueous preparations for indoor applications; here also sorbic acid and its salts are used. U.S. Pat. No. 4,585,795 discloses the use of mixtures of alkali metal salts of organic acids in combination with selected quaternary ammonium salts for protecting wood from mold attack. JP-A 100 67 607 describes a wood insecticide which contains, as active ingredient, at least one C6-C12 fatty acid in amounts between 0.01 and 9% by weight. WO-A 96/11572 describes compositions of carboxylic acids having up to 10 carbon atoms and their salts and C3-C10 diols or esters of these compounds for cleaning, disinfection, surface treatment, impregnation or antimicrobial treatment.
If wood is treated, for example with solutions of the abovementioned substances, after drying the solution, the previous treatment in most cases is no longer readily detectable. However, for a quality assessment, for further processing and commerce, it is of critical economic importance. Although a treatment can be detected by testing an individual product, this is accompanied by complex chemical analysis and processing. For this the appropriate preservative must, in a complex procedure, be isolated from the wood (for example by extraction with organic solvents), concentrated, identified and quantitated. The results obtained can only be related to the product examined. Large amounts of machined wood or wood in assembled products (for example pallets) in the industrial sector or hand craft sector (such as unworked furniture timber) or the home worker sector may not be examined as a whole. In addition, when the abovementioned methods are used in wood-processing factories, because of the high throughput rates frequently it is not possible to test whether the worked wood has been sufficiently treated at all points, quite apart from the fact that apparatuses for carrying out such testing are expensive and the tests themselves can generally only be carried out by qualified specialists. Such an expenditure is not justified in most cases.
It has already been proposed to add an indicator to the solutions of organic acids or their salts used for wood treatment. Such indicators are prescribed, for example, in DE-A 196 11 868 as a marking agent for timber. However, for this purpose chemical reactions are always used (intensely colored azo dyes are formed in DE-A 196 11 868). Not only the substances used but also the chemicals required for the coupling are generally of toxicological concern. Furthermore, only point tests can be performed using this method and lead to staining at the points of study.
WO-A 02/17717 describes a fluorescent agent which indicates whether water intended for use with flowers has been adequately supplied with appropriate treatment agents for cut flowers.
EP-A 0 950 700 describes the use of optical brighteners in aircraft de-icing compositions for improving the detection of the use of de-icing compositions.
There is still a requirement for a simple, inexpensive and rapidly performed test which gives information as to whether wood has been appropriately treated or not.